I don’t know where Breitbart gets the ‘open borders’ thing from, since the UK does not have open borders with the rest of the EU now. It’s never been part of the Schengen open-borders zone, which only includes some EU countries plus Norway and Switzerland..Breitbart is getting confused with the rights of existing EU citizens from other EU countries to live and work in the UK. That doesn’t apply to people from countries outside the EU, whether they arrive from Europe or from elsewhere. Immigration from those othrer countries is entirely within the control of the UK Government, as it always has been, not the EU.
The U.K. is letting people from the Middle East and Africa in with no checks.
I am not sure where you are getting the idea there is no open border to let in the migrants?